Machine for injection molding of selfhardening resins



April 2, 1963 J. BICHL 3,083,408

AMACHINE FOR INJECTION MOLDING OF SELF-HARDENING RESINSl Filed NOV. 18,1958 2 Sheets-Sheet 1 April 2, 1963 J. BxcHl. 3,083,408

MACHINE FoR INJECTION MoLDING oF sELE-HARDENING RESINS Filed Nov. 18,1958 2 Sheets-Sheet 2 3,083,4tl3 MACHENE FR EUECHIQ MQLDNG @il HARDENENG.inset Bielli, Hans am Moos, Graham-Amper, Germany Filed Nov. 18, 1958,Ser. No. 774,621 Claims priority, application Germany Nov. 2i, 1957 ZClaims. (El. ILS-3i?) A number of attempts have been made to injectionmold or process in injection molding machines self-hardening syntheticresins lby means of the rim-retaining, vacuum sac, pressure sac orvacuum press process or various processes in which superatmosphericpressure is employed. All attempts have failed due to the self-hardeningproperties of the synthetic resin, which tended to weld, bond andadhesively connect relatively movable solid surfaces contacting eachother. The occurrence of such surfaces cannot be avoided in theprocessing or" selfhardening synthetic resins in machines because thesynthetic resin mus-t somehow be conveyed and directed, which is alwaysperformed by machine members which Vhave moving and mutually contactingsurfaces, whether these machine members consist of metals, plastics,ceramics, fiber material, rubber or the like. Whenever self-hardeningsynthetic resins can enter into the gaps necessarily existing betweenrelatively movable surfaces contacting each other, a resin hlm willform, which hardens immediately so that the machine members formingthese surfaces Will bind each other. This lm will also be formed betweenparts, which have been ground one in the other so that the gaps aremicroscopically small, because the resin is under high pressure and willpenetrate even into gaps between machine members ground one in theother. Once the resin has penetrated between the parts, the etiect ofthe hard film will be the worse the iiner is the gap. -For the samereason it has not been possible to use valves for controlling the owingmass of the synthetic resin, particularly to divide, stop or start it.

A solution of the difficulties thus characterized is afforded by theprocess proposed by the invention for injection molding self-hardeningsynthetic resins, which may contain iillers such as glass ibers andtextiles, by keeping the synthetic resin separate from all movablebody-dening surfaces by iiexible holding means which are non-reactivewith respect to the self-hardening synthetic resin throughout the rangein which movable bodydelining surfaces are encountered, and in which thesynthetic resin is in a condition in which it would 'be likely toharden. The synthetic resin will be in a self-hardening conditionwhenever the period of time required is suficient. This will always bethe case when the synthetic resin is not displaced by freshly suppliedsynthetic resin.

The application of this process to the synthetic resin supply involvesthe provision of an apparatus which is characterized by the provision ofa diaphragm or sac of exible material, which is non-reactive with thesynthetic resin and which serves for confining the synthetic resinsupply in a reservoir positioned in front of the injection head of theinjection molding machine, to prevent the synthetic resin from wettingthe inside walls of the machine.

Also of importance is the provision, in the injection head, of a guidesurface of ilexible material which is 1i ted non-reactive with theplastic -in the injection chamber of the machine, to prevent thesynthetic resin from wetting the boundary walls which deflect thesynthetic resin from the inlet of the injection chamber to the outletthereof. This is of special importance when a cutting means must beprovided in the injection chamber, which means must be moved and drivento cut iller ibers, particularly of glass or textile material. Thiscutting means may comprise rotary cutter blades or reciprocating shearrams. vIn this case the provision of said guide surfaces of #flexiblematerials which are non-reactive with respect to the synthetic resin,particularly of polyvinylchloride and its derivatives, is essential toenable the use of cutting means having such movable surfaces. Owing toits resiliency the exible material which prevents the self-hardeningsynthetic resin from wetting the gaps that are necessarily formed, suchmaterial follows readily the reciproca-ting movement, e.g., of a shearram, and is also capable of applying itself closely to the rotatingmachine parts so that the synthetic resin cannot penetrate into gapsthus protected. For this reason the invention is essential for the useof such rotary or reciprocating cutting means.

The -drawing shows illustrative embodiments of the invention.

vFIG. l is a longitudinal sectional view showing the improved reservoirand injection head of an injection molding machine of a usual type;

FlG. 2 is a vertical sectional view of a modified reser- Voir;

FIG. 3 is a sectional view of another form of such reservoir;

FlG. 4 shows a modiiied form of injection head in longitudinal section;

FIG. 5 is an elevation of the cutter blade mounted for rotation in theinjection head; and

IFIG. 6 is an elevation, partly in section, of an injection moldingmachine according to this invention.

in FIG. l, il denotes the reservoir of the synthetic resin injectionmolding machine. The reservoir carries in the usual manner an upwardextension 2, which contains the driving piston 3 or the press ram 4,which serves for exelling the synthetic resin from the reservoir and fortransferring it into the injection head of the injection moldingmachine. By means of the connections 5 and 6 the driving piston may besubjected in a manner known per se to the action of a working fluidunder pressure, such as pressure oil or compressed air. The reservoir lis conected in the usual manner by the yflange connection 7 to thesupply conduit 8 leading tothe injection head 9 of the injection moldingmachine. n

It this device for transferring synthetic resin from the synthetic resinsupply lill to the injection molding machine were not constructedaccording to the invention it would not be suitable becauseself-hardening synthetic resins would immediately penetrate into theannular gap between the piston 4 and the cylinder 1 to form there ahardened resin iilm, .so that the piston 4 would bind in the cylinderll.

This is prevented according to the invention by enclosing the supply lllof self-hardening synthetic resin with a diaphragm or sac lll of aflexible material which will not bond with the supply of self-hardeningsynthetic resin 16. These requirements are met by certain syntheticresins V32, next to which the injection molding die 25 engagement withthe blade counterplate.

accesos such as polyvinylchloride and its derivatives. Thus, the sac 11precludes any penetration of sel-hardening synthetic resin between parts4 and l. On the other hand, the sac 11 is compressible so that thesynthetic resin forced out ofthe cylinder by the press ram d can enterthe transfer conduit `8 leading to the injection head 9 withoutdiiculty.

The injection head itself forms `an injection chamber l2, which has aninlet 13 for the synthetic resin mass forced in from the transferconduit S and an outlet mouthpiec 14, which serves for guiding -a shearram i5, which is also actuated by means of a piston 16. The piston le isagain under the action of a pressure fluid, which is controlled by knownmeans to permit of a reciprocation of the shear ram 15. The shear ram 15is guided by the itting i7, whici may consist, eg., of Tellen(polytetrailuoroethylene). The guide member 1S provided for directingand guiding the synthetic resin entering through parts 8, i3 consistsalso of flexible material which does not bond with and is non-reactivewith respect to the self-hardening synthetic resin. The guide member lhas beadlilce enlargements 19 and 20, which serve to locate the guidemember i8 between the parts 9 and i7 and on the sh,ar ram i5. To enablethe guide member 18 to be located between parts 9 and 17 the injectionhead chamber 9 has an end Ymember 2i whereby the bead i@ can be stressedbecause parts 9 and 2l are interconnected by screw threads ZZ. A groove23 receiving the bead Zt) is suicient for locating the guide member i8on the shear` ram i5 by means of the be-ad 2i?. Serving to guide .theshear ram J5, the guide member ig thus follows the reciprocatiou of theshear ram 1S and prevents any wetting of the tting i? and of the shearram 15 on surfaces which are moved and contact each other during theoperation of the injection molding machine. The portions of thesynthetic resin mass which `are divided oli by the shear ram 1.5 passthrough the connection opening to the injection molding die 25.

In FIG. 4, 9 is again the injection chamber having the inlet opening 13for the synthetic resin. The mouthpiece 26 is different in construction,having four inlet ducts Z7, 2S, 29, Sil, which are shown in more detailin FiG. 5. These ducts combine at 3i. to form the ejection opening isagain disposed. A blade counterplate 33 disposed in front of themouthpiece 26 has openings registering with the ducts 2730 and havingthe same references as the latter. The rotary blade 3dhaving cuttingedges 3S, Se, 37, 38 is in The rotary blade 3ft is driven by the bladeshaft 39 rotatably mounted in the bearing member eti. The bearing memberdo and the blade shaft 39 are also protected by a guide member 41 frombeing wetted by the self-hardening synthetic resin adjacent to therelatively moving contact surfaces. ri`he guide member 4l has againbeads d2 and d3, by which it is located on the wall of the injectionchamber g' and the blade-driving shaft 39. For this purpose the bladeshaft 39 has a groove 44 which receives the bead.

FIG. 2 shows the different embodiment oi the reser- Voir. In this caseiiexible materials which do not bond with the self-hardening syntheticresin are also used for pressurizing the synthetic resin. 'Ihere isagain a reser voir 45 having a connection 46 to the conduit d. lI'hereservoir is bipartite and forms a parting joint 49, which is adjoinedby the gripping rings 5t), 5i for gripping the saclike diaphragm 52,which consists again of flexible material which is non-reactive withrespect to the self-hardening synthetic resin lll. A pressure fluidsupplied at 53 acts on the diaphragm in the space 5d and causes theself-hardening synthetic resin to emerge out of the conduit 48 withoutbeing capable of wetting valves disposed before the connection 53 andhaving moving surfaces in contact with each other to that these valveswould become inoperative it the self-hardening synthetic resin hadaccess to them` FIG. 3 shows another embodiment, in which the sac 55' offlexible material is gripped between the base part S6 and the top part,which forms at the same time the wall of the reservoir. The base part Sehas a concave depression 58 so that the supply oi self-hardening resinill can be accommodated between the base part 55 and the sac 55. Endmembers S9, dil close the structure toward the outside. i is again aconnection to the conduit S. Valvecontrolled conduits are connected at62 so that an access of self-hardening synthetic resin to the movedvalve surfaces must be prevented. rihis is achieved by the provision ofthe sac 55.

EEG. 6 shows an injection molding machine which is constructed accordingto the invention and comprises a revolving table 63 for four dies 25',which may be replaced by any other number of dies, of course. Therevolving table 63 is driven bythe electric motor 64 through theintermediary of the pinion 65 and the gear rim 66 to move any of thedies selectively to a position in which it registers with the injectionhead 2l (see FIG. 4). The dies, which may be bipartite, as is indicatedat 25a and Zb, are under the iniiuence of a hydraulically effectiveclosing and opening device, which is arranged under the closed hood 717of the machine. This hood is shown broken away at 7i. The cylinder 67 isshown, which is supported by the lined beam 6b and contains the pressram. The drawing shows also the movable beam 69, which is guided oncolumns 72. The movable beam d@ carries the top part @25a of the diewhereas the base part 5b is held at 7d on the stationary lowercross-beam 73. The injection head Zi with the guide cylinder 9 for thepress ram i6 are accommodated in a lateral extension 75 of the machinedrame. This extension accommodates also the other parts shown in FiGS. land 4. The connecting liange for the transfer conduit 8 leading from thereservoir il to the injection head 2li is apparent at 7. Extendingaxially from the connecting ilange 7 the reservoir 1t is apparent onlyin EEG. 6 rather than in FlG. l. 77 is the control station of themachine, comprising the switches 7 the measuring instruments 79 and therelays (not shown) as well as the terminals for and junctions of theelectrical conductors. The switches 7S serve for controlling thehydraulic press rams 67 and 347 and .i6 and for energizirnT anddeenergizing the electric motor 64.

These self-hardening resins when cured, are characterized by across-linked network of polymeric chains.

it is understood that the inventor intends to claim, as a part of hisinvention, any variation, substitution and changes that lie within thescope of the invention and the hereinafter appended claims and intendsto include within the scope oi said claims such changes as may beapparent to those skilled in the art in the practice o the principles ofthis invention and Within the scope as set forth in thehereinabove-stated specification.

What is claimed is:

l. An injection molding machine for injecting a selfhardening syntheticresin into a mold, said machine comprising a cylinder, a sac-likediaphragm of inert nonietallic exible material peripherally attached tothe front end of the cylinder and adapted to receive said resin and toshield the inside wall of the cylinder therefrom, said diaphragm beingin close face-to-face contact with the inside wall of the cylinder,means for exerting a continuous and unidirectional pressure upon thesaid diaphragm to expel suiiicient resin therefrom to till the entiremold, a res'm delivery conduit leading from the front end ci thecylinder, and an injection head connected to said conduit, said headhaving a chamber in communication with said conduit, a mouthpieceforming the front wall of said chamber, a plunger guided forreciprocation in said chamber to push the resin through said mouthpiece,and a iiexible member of inert material peripherally attached to therear portion of the inner wall of the head and centrally fastened to theplunger at the frontend thereof. j

2. An injection molding machine for injecting a selfhardening syntheticresin into a mold, said machine comprising a cylinder adapted to containa charge of said resin, a diaphragm of inert eXible materialperipherally at- 'cached .to the inside wall of the cylinder forshielding said Wall from the resin, a plunger slidable in the cylinderfor exerting a forward force upon Jthe rear side of the diaphragm ttocause the diaphragm to push the resin in front of it, a resin deliveryconduit connected to the front end of .the cylinder, ian injection headhaving a chamber in communication with the conduit, a mouthpiece at thefront end of said head, a plunger guided for reciprocation in saidchamber, and a guide member of inert exible material peripherallyfastened to the inside wall of Ilthe head and centrally fastened tothefront end of the plunger for shielding the rear parts of the plungerfrom the resin.

References Cited in the file of this patent UNITED STATES PATENTSlIeilery .Tune 21, IFields Nov. 21, Wacker Aug. 17, Wacker Ian. 4,Spanier June 24, Hawk June Clifford et al. Aug. 28, Hendry Apr. 5,Tavola June 19, Keaton et a1. May 21,

FOREIGN PATENTS Australia Aug. 11,

Belgium Feb. 15,

2. AN INJECTION MOLDING MACHINE FOR INJECTING A SELFHARDENING SYNTHETICRESIN INTO A MOLD, SAID MACHINE COMPRISING A CYLINDER ADAPTED TO CONTAINA CHARGE OF SAID RESIN, A DIAPHRAGM OF INERT FLEXIBLE MATERIALPERIPHERALLY ATTACHED TO THE INSIDE WALL OF THE CYLINDER FOR SHIELDINGSAID WALL FROM THE RESIN, A PLUNGER SLIDABLE IN THE CYLINDER FOREXERTING A FORWARD FORCE UPON THE REAR SIDE OF THE DIAPHRAGM TO CAUSETHE DIAPHRAGM TO PUSH THE RESIN IN FRONT OF IT, A RESIN DELIVERY CONDUITCONNECTED TO THE FRONT END OF THE CYLINDER, AN INJECTION HEAD HAVING ACHAMBER IN COMMUNICATION WITH THE CONDUIT, A MOUTHPIECE AT THE FRONT ENDOF SAID HEAD, A PLUNGER GUIDED FOR RECIPROCATION IN SAID CHAMBER, AND AGUIDE MEMBER OF INERT FLEXIBLE MATERIAL PERIPHERALLY FASTENED TO THEINSIDE WALL OF THE HEAD AND CENTRALLY FASTENED TO THE FRONT END OF THEPLUNGER FOR SHIELDING THE REAR PARTS OF THE PLUNGER FROM THE RESIN.